Gasification of carbonaceous materials



March 2, 1954 R. J. MORLEY GASIFICATION oF cARBoNAcEoUs MATERIALS Filed March 26, 1951 LII..

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Ronald JamesMgy,

iM/f7 f u, (M ATTORNEYS.

Patented Mar. 2, 1954 GASIFICATION OF CARBONACEOUS MATERIALS Ronald James Morley, Norton-on-Tees, England,

assigner to Imperial Chemical Industries Limited, a corporation of Great Britain Application March 26, 1951, Serial No. 217,675

Claims priority, application Great Britain April 24, 1950 3 Claims. (Cl. 48-197) This invention relates to processes for the gasification of solid carbonaceous materials and more particularly to such processes in which the solid carbonaceous materials are employed in particulate form.

In these processes for carbonising, for example coal, and/or for the production of gaseous mixtures by the interaction of an oxygen-containing gas and/or steam with hot carbonaceous material, for example coke, the heat required for the carbonising and/or gas producing step or steps is, in general, obtained .by the partial combustion of similar carbonaceous material by subjecting it to the action of an oxygen-containing gas at a rate suicient to maintain the particles in the desired state of fluidisation and to give the desired rate and degree of combustion, then passing hot particulate material from this combustion step to the carbonisation and/or gas-producing step or steps.

The sensible heat contained in the gaseous products of combustion however is not in a form which can be directly utilised in the process. For example, when cold air is used in the combustion of particulate coke in the uidised state, and the quantity of coke in the uidised mass is suflicient to limit the temperature of the coke and the products of combustion to about 1000 C., such quantity of coke being dependent upon the proportion and properties of ash present in it,

the amount of heat absorbed by the coke will be about 60% of the total heat produced, the remaining 40% being carried out of the combustion step with the gaseous products.

It is clearly advantageous to decrease the proportion of the total heat produced in the combustion step which is lost in the gaseous products from that step. It is likewise an advantage to decrease the heat lost in the gaseous products from the other steps of the process.

To this end it has already been proposed to bring the gaseous products from the combustion or other steps of such processes into indirect heat exchange, for example' in conventional tubular or plate type heat exchangers, with the gases and/or vapours being passed to the process.

I have found that the heat in the gaseous products from a combustion or other step of such processes may be more advantageously used to preheat incoming gases and/or vapours, for example the oxygen-containing gas supplied to the combustion step whereby a much higher percentage of the heat produced in this step is made available to the process, if such Apreheating is carried out as hereinafter described.

Moreover, the method of the present invention is particularly advantageous in the carbonisation and/ or gasication processes above mentioned as it ensures a much higher utilisation of the heat produced than is possible by the methods 'of thev prior art and permits continuity of operation as the heat exchange apparatus does not become fouled with dust.

According to the present invention there is provided, in a process for the carbonisation and/or gasification of particulate solid carbonaceous material maintained in the uidised state, the method of preheating incoming gases and/or vapours which comprises passing the hot gaseous products from a step of the process upwardly through a vessel in countercurrent flow to a mass of solid material in the form ofpebbles moving downwardly under gravity through the vessel, whereby the pebbles are heated and the gaseous products are cooled, then passing the heated pebbles downwardly under gravity through an interconnecting conduit and into a second vessel down which the pebbles move, under gravity, and countercurrently to an upwardly owing stream of the incoming gas and/or vapour, whereby the pebbles are cooled and the incoming gas and/or vapour is heated and subsequently passed to any desired step of the process.

It will be understood that the dimensions of the interconnecting conduit between the vessels should be such as to provide, when the conduit is full of downwardly moving pebbles, su'icient pressure drop to prevent substantial flow of gas and/or vapour from thelower into the upper vessel. Y. H

The arrangement of two vessels through which solid material is caused to ow countercurrently to gas and/or vapour for the purpose of heat ex-4 change, as above described, will hereinafter be referred to as a set of pebble-heaters.

The cooled pebbles leave the second vessel at the bottom and are returned to the top of the iirst vessel either directly or indirectly by any suitable means, for example a bucket elevator, the rate of iiow of the pebbles through the vessels being regulated to give the desired cooling ofthe gaseousiproducts from the process and the desired preheating of the incomingV gas and/or vapour.

As a further feature of the presentinvention the method of preheating incoming gases and/or vapours, as above described, is applied to at least two steps of a process for the carbonisation and/or gasification of particulate solid carbonaceous material maintained in the luidised state, one of said steps being a combustion step, and at least some of the pebbles used in the sets of pebble-heaters are exchanged between them in such manner that carbonaceous matter, for example tar, which may have been deposited on the pebbles when recovering heat from the gaseous products from a gasification or carbonisation step, will be removed by combustion as the pebbles are passed through the pebble-heater employed for preheating the air or other oxygen-containing gas being fed to the combustion step.

The exchange of pebbles between the sets of pebble-heaters may be continuous'or intermittent as desired. It has been found convenient, for this purpose and for the control of theeuantities of pebbles to be exchanged between the two or more sets of pebble-heaters, to raise the cooled pebbles leaving the bottom of the second vessels of the sets of pebble-heaters, for example by means of a bucket elevator, and to discharge them into a separate hopper or bin for each pebbleheater-and to redistribute them as desired from these hoppers or bins to the tops of the rst vessels of the sets of pebble-heaters.

The' pebbles may be of any solid material which is,v sufficiently refractory to withstand the" operatingV temperatures, for example U0 C. to IOC., and the repeated'hating and cooling. Examples of suitable materials are alumina and mullitel The termpebble as used in this specification is to be understood to mean bodies oi such aV shape as to permit flow by gravity. They may be ovoi'dal or spheroi'dal or only roughly ovoidal or spheroidal;v preferablythey should'have substantially smooth surfaces but it is possible to usr.x materials with rough facesv andv sharp edges; Substantially spherical pellets or balls of uniform site and'shape formed of mullite have been found to be particularly suitable for use in the method of the'prese'nt invention.

Alternatively certain naturally occurring materials and minerals may be used' when suitably prepared byA such methods as crushing and screening, Although in general such naturally occurring rr'iaterialsl will have refractory properties inferior to those of such materials as alumina, and mullite, nevertheless the greater loss due to breakage andspalling might be tolerated because'of the relative cheapness of the material. The size of such bodies may be varied over a wide-range, for example 11e to 34" in In'ean diameter but it is preferred to use balls of about diameter.

The method of heat recovery of the present invention is illustrated in the accompanying drawing' which diagrammatically shows a plant for the carbonization and gasification of particulate solid carbonaceous material, said plant comprising a carbonization zone, a gasification zone, a combustion zone and a heat recovery system of two setlsof pebble-heaters. In operation, a portion of the heat required in the carboniaation and/or the gasification zone is supplied byv the passage f'hot', partially burnt particulate carbonacous iate'rial fromrthe combustion' zone te the oarbonizationand/or easincation zoiie. Hot gaseous products from at least one of the combustion, carboni'zation and gasification zones are passed upwardly through the upper vessels of the illustrated sets of pebbleheaters where they are cooled by heat interchange with the pebbles passing downwardly therein. Oxygen-containing gas is passed upwardly through the lower vessel of oneY of the sets' of pebble-heaters where it is preheated by' heat interchange with the heated pebbles passing siii downwardly from the upper vessel, the heated oxygen-containing gas being then passed to the combustion zone. The gas or vapor required for the carbonization and/orv gasification zone is passed upwardly through the lower vessel of the other set of pebble-heaters where it is preheated by heat interchange with the heated pebbles passing downwardly therein, the heated gas beingV then passedto the gasication and/or carboni'zation zone. Cooled pebbles leave the bottomof the` lower vessel in each set of pebbleheaters and are/elevated to a feed hopper positioned above the-upper vessels of the sets of pebble-heaters. The pebbles are then passed fromthe feed hopper to the two sets of pebble heaters `in the quantities desired.

The method of the present invention is further illustrated in the following example, which describes the preheating of air for use in a combustion step Aby means of heat recovered from the gaseousproducts of the same step.

Example In a'p-lant'for' the production' of water gas in which hot particulate carbonaceous material is transferred from' a combustion step t0 the gasproducingfstep, tnefgaseoas products ci combustionamounting-*to about'sf cubic metres per hour, measured at room temperature and pressure, at a temperature of i050 C. were led to the base of a 2K9 internal diameter by 3'0"'long vessel and int-o the top of the vesselthe're were fed mullite balls'of'f'e" Vdiameter'a't the rate of i kilograms per' hour. in passing countercurrently toetheznul'lite' ballslthe gaseous combustion products werev cooled' toV 240ci C. and the mfullite balls werefheate'd from about 100`C, to 9 59'J C. he'nnillite` balls leaving" the bottom of the'v'ess'el were passed byV gravityV through a, 3" bore pipe, 30'Df long to a second vessel OfYZ diameter by 56 long Idown which they fiowed under gravity. Air' at atmospheric temperature was fed, at the'r'ateA of 860 cubc'metres per hour, measured at room temperature and pressure, into the bottom ofthe'second vessel and was withdrawn from the top ofthis vessel at a temperature of 909 CL andy Aled' to` the combustion step of the process. The mullite balls leaving the bottoin ofthe secondf vesselA had been cooled toabout C; and were'returned to the top of the rst vessel' by means of a' mechanical elevato.

The heat recovered in this way was absorbed in the combustion' step by' increasing the amount of particulate cokey and ash nuidised per unit duantity'of the air' fed'to the combustion step and the heat recovered wasY thusk made'available forproducing watergas 'when the hot particulate coke was transferred tol the gas-producing step in which thev hot solids' were brought into contact Withstaln.

with the heat thus recovered 88% of the man heat liberated in thecombust'ion step wasV made availame to thepro'cess;

The' method of the present invention is particularly advantageous in the processes hereinbefore described, as' the heat exchange apparatus does not become fouled with dust contained in the gaseous'combustion'and reaction products and as it is perfectly continuous and in consequence avoids disturbances in the flow of the gaseous reactants through the plant, thus ensuring striooth operation of such processes.

The term gas as used in this specification' and/or in the appended claims is' to be understood to mean substances lwhich are gaseous 5 under normal conditions of temperature and pressure, normally liquid substances in Vaporised form, and mixtures of these.

I claim:

l. In processes for the carbonization and gasification of particulate solid carbonaceous material by interacting gas with hot particulate carbonaceous material maintained in the fluidized state, said hot particulate carbonaceous material being partially burnt in a combustion zone by subjecting it to the action of an oxygen-containing gas at a rate suicient to maintain the particles in the fluidized state and to give the desired rate and degree of combustion, then being passed to at least one of a carbonization zone wherein there is maintained a fluidized mass of particulate carbonaceous material being carbonized, and a gasication zone in which a iiuidized mass of particulate carbonaceous material is being gasiiied by interaction with gas, the method of recovering heat which comprises passing hot gaseous products from a step of the process upwardly through the upper Vessel of a first set of p-ebble-heaters, passing a mass of solid material in the form of pebbles downwardly under gravity through said first set of pebble-heaters, passing a gas upwardly through the lower vessel of said rst set of pebble-heaters and then to a gas producing step of the process other than the combustion step, elevating pebbles from the bottom of said iirst set of pebble-heaters to a hopper above its upper vessel, passing at least some of the pebbles from said hopper into said upper vessel of the rst set of pebble-heaters and the remainder into the upper vessel of a second set of pebble-heaters, passing hot gaseous products from a step of the process upwardly through the upper vessel of said second set of pebble-heaters,

passing a mass of solid material in the form of pebbles downwardly under gravity through said second set of pebble-heaters, passing an oxygencontaining gas upwardly through the lower vessel of said second set of pebble-heaters and then to the combustion step of the process, elevating pebbles from the bottom of said second set of pebble-heaters to a hopper above its upper vessel, passing at least some of the pebbles from said hopper into said upper vessel of the second set of pebble-heaters and the remainder into the upper vessel of the iirst set of pebble-heaters.

2. A process as recited in'claim 1 in which the oxygen-containing gas is, air.

3. A process as recited in claim 1 in which the exchange of pebbles between the sets of pebbleheaters is continuous.

RONALD JAMES MORLEY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,447,306 Bailey et al. Aug. 17,1948 2,519,315 Johnson et al Aug. 15, 1950 FOREIGN PATENTS Number Country Date 586,391 Great Britain Mar. 18, 1947 625,879 Great Britain July 5, 1949 626,743 Great Britain J'uly 20, 1949 

1. IN PROCESS FOR THE CARBONIZATION AND GASIFICATION OF PARTICULATE SOLID CARBONACEOUS MATERIAL BY INTERACTING GAS WITH HOT PARTICULATE CARBONACEOUS MATERIAL MAINTAINED IN THE FLUIDIZED STATE, SAID HOT PARTICULATE CARBONACEOUS MATERIAL BEING PARTIALLY BURNT IN A COMBUSTION ZONE BY SUBJECTING IT TO THE ACTION OF AN OXYGEN-CONTAINING GAS AT A RATE SUFFICIENIT TO MAINTAIN THE PARTICLES IN THE FLUIDIZED STATE AND TO GIVE THE DESIRED RATE AND DEGREE OF COMBUSTION, THEN BEING PASSED TO AT LEAST ONE OF A CARBONIZATION ZONE WHEREIN THERE IS MAINTAINED A FLUIDIZED MASS OF PARTICULATE CARBONACEOUS MATERIAL BEING CARBONIZED, AND A GASIFICATION ZONE IN WHICH A FLUIDIZED MASS OF PARTICULATE CARBONACEOUS MATERIAL IS BEING GASIFIED BY INTERACTION WITH GAS, THE METHOD OF RECOVERING HEAT WHICH COMPRISES PASSING HOT GASEOUS PRODUCT FROM A STEP OF THE PROCESS UPWARDLY THROUGH THE UPPER VESSEL OF A FIRST SET OF PEBBLE-HEATERS, PASSING A MASS OF SOLID MATERIAL IN THE FORM OF PEBBLES DOWNWARDLY UNDER GRAVITY THROUGH SAID FIRST SET OF PEBBLE-HEATERS, PASSING A GAS UPWARDLY THROUGH THE LOWER VESSEL OF SAID FIRST SET OF PEBBLE-HEATERS AND THEN TO A GAS PRODUCING STEP OF THE PROCESS OTHER THAN THE COMBUSTION STEP, ELEVATING PEBBLES FROM THE BOTTOM OF, SAID FIRST SET OF PEBBLE-HEATERS TO A HOPPER ABOVE ITS UPPER VESSEL, PASSING AT LEAST SOME OF THE PEBBLES FROM SAID HOPPER INTO SAID UPPER VESSEL OF THE FIRST SET OF PEBBLE-HEATERS AND THE REMAINDER INTO THE UPPER VESSEL OF A SECOND SET OF PEBBLE-HEATERS, PASSING HOT GASEOUS PRODUCTS FROM A STEP OF THE PROCESS UPWARDLY THROUGH THE UPPER VESSEL OF SAID SECOND SET OF PEBBLE-HUEATERS PASSING A MASS OF SOLID MATERIAL IN THE FORM OF PEBBLES DOWNWARDLY UNDER GRAVITY THROUGH SAID SECOND SET OF PEBBLE-HEATERS, PASSING AN OXYGENCONTAINING GAS UPWARDLY THROUGH THE LOWER VES- 